Robustness Analysis of Quantum State Transfer through Spin-Chain in Diamond for Room-Temperature Quantum Computing

The quantum information as expressed by the spin-state of qubits in quantum computers needs to be transferred among qubits reliably with fidelity. This work examines the robustness of quantum state transfer (QST) via a one-dimensional spin-chain in the diamond formed by implanted nitrogen (N) atoms between qubits (or quantum registers) realized by N-V (nitrogen-vacancy) centers. The effect on QST fidelity of both uneven-ness in spin sites along the spin-chain and the lack of rotational symmetry of the chain is examined by numerical simulation. The theoretical approach for the analysis of spin chain is through the Jordan-Wignar transformation from the spin entities to fermions to simplify the mathematical complexity and to give a clear physical picture. The conclusions from this investigation are: 1) the QST via spin-chain is insensitive to the deviation of spin-location from their uniform spacing; 2) the broken rotational symmetry has big impact on the fidelity of QST. SWAP quantum gates for swapping bit information on two qubits linked by the spin-chain is used as an example for the analysis. The prospect and progress of using N-V centers in diamond for the realization of room-temperature quantum computers are finally reviewed in this talk.